Circuit breakers are one of a variety of overcurrent protection devices used for circuit protection and isolation. The circuit breaker provides electrical protection whenever an electric abnormality occurs. In a typical circuit breaker, current enters the system from a power line and passes through a line conductor to a stationary contact fixed on the line conductor, then to a movable contact. The movable contact is fixedly attached to a pivoting arm. As long as the stationary and movable contacts are in physical contact, current passes between the stationary contact and the movable contact and out of the circuit breaker to down-line electrical devices.
In the event of an overcurrent condition (e.g., a short circuit), extremely high electromagnetic forces can be generated. The electromagnetic forces can be used to separate the movable contact from the stationary contact. Upon separation of the contacts, an arcing condition occurs. The breaker's trip unit will trip the breaker which will cause the contacts to separate.